Dawei gbase8s cursor stability read esql test case

GBase8s Cursor stability read

Basic database table creation

create database db03 with log;

create table customer(
	fname char(9),
    lname char(9)
);

insert into customer values('a','A');
insert into customer values('b','B');
insert into customer values('c','C');
insert into customer values('aa','AA');
insert into customer values('bb','BB');
alter table customer lock mode (row);

Cursor stability reads rows

#include <stdio.h>
#include <unistd.h>

EXEC SQL define FNAME_LEN 15;
EXEC SQL define LNAME_LEN 15;
main()
{
    
  EXEC SQL BEGIN DECLARE SECTION;
  char fname[ FNAME_LEN + 1 ];
  char lname[ LNAME_LEN + 1 ];
  EXEC SQL END DECLARE SECTION;

  printf( "DEMO1 Sample ESQL Program running.\n\n");
  EXEC SQL WHENEVER ERROR STOP;
  EXEC SQL connect to 'db03';

  EXEC SQL DECLARE democursor cursor for
  select fname, lname
  into :fname, :lname
  from customer
  where lname < 'C'  ;
  EXEC SQL execute immediate 'BEGIN WORK';
  EXEC SQL execute immediate 'SET   ISOLATION   TO   CURSOR  STABILITY';

  EXEC SQL open democursor;

  for (;;)
  {
    
    getchar();
    EXEC SQL fetch democursor;
    if (strncmp(SQLSTATE, "00", 2) != 0)
      break;
    printf("%s %s\n",fname, lname);
  }

  if (strncmp(SQLSTATE, "02", 2) != 0)
    printf("SQLSTATE after fetch is %s\n", SQLSTATE);

  EXEC SQL execute immediate 'COMMIT WORK';
  EXEC SQL close democursor;
  EXEC SQL free democursor;
  EXEC SQL disconnect current;
  printf("\nDEMO1 Sample Program over.\n\n");
}
        

explain ： perform cs.exe Program , Every time you press “ enter ”, The cursor of the program will point to a row of data , At this time, this row of data will be locked by sharing , Others can't modify this line of data . When the cursor points to the next row of data , The previous row of data can be modified .

testing procedure ：

result	conversation 1：	conversation 2：	window 3：
	./cs.exe
	“ enter ”
			onstat -g sql You can see CURSOR STABILITY Isolation level . onstat -k It can be seen that only the second 1 The line is locked , Other rows are not locked .
Lock error update Execution failure		update customer set lname=‘A1’ where fname=‘a’ ;
update Successful implementation		update customer set lname=‘B1’ where fname=‘b’ ;
	“ enter ”
			onstat -g sql You can see CURSOR STABILITY Isolation level . onstat -k It can be seen that only the second 2 The line is locked , Other rows are not locked .
update Successful implementation		update customer set lname=‘A2’ where fname=‘a’ ;
Lock error update Execution failure		update customer set lname=‘B2’ where fname=‘b’ ;